It is common to limit access to physical locations through access control systems. The access control system can vary in complexity from a latch a child cannot reach to biometrics such as a fingerprint or retina reader. Some of the more common systems include proximity cards and other credentials, where the card or other credential is linked to a particular individual.
In a high security environment, a number of strategies may be employed to ensure that a physical access control system maintains an accurate record of users' current location. The system can thereby determine if an access attempt inconsistent with the purported location of the user is being made and then take appropriate action. One method that an authorized user may use to “assist” a fellow worker which would be inconsistent with the intended security is to go through a gate or turnstile using their proximity card and then pass the card back (“pass back”) to someone else to use. Another method is for a user to hold open a door to allow a fellow worker to gain access without using their card (“tailgating”).
As described in the “Detailed Description of the Invention” section, the system can have methods to deter users from participating in pass back or tailgating activities, such as notification or preventing access.